In recent years, a technology to determine the movement of a person on the basis of an image captured by an image capturing device has been developed. This kind of technology includes a technology to determine the orientation of a person. For example, in a proposed technology, principal component analysis is conducted on the data of a layer of a shoulder which is extracted from 3D scan data of a subject, and the second principal component is determined as the “direction of body”. Also, there is a technology to determine whether a person pays attention to a specific region such as a store shelf. For example, in a proposed technology, a face is detected from a region of a moving object that is detected on the basis of an image and measured person position data, and the sight line direction is calculated from the detected face image, to thereby determine the attention position of the person. See, for example, Japanese Laid-open Patent Publication 2012-215555, and Japanese Laid-open Patent Publication 2007-286995.
In the meantime, one may conceive of a method to determine the orientation of a person on the basis of the sight line direction calculated as above. However, in this method, since the sight line is unable to be captured when the person wears glasses or sunglasses for example, there is a problem that the situation that allows the orientation of the person to be determined is limited.